Relative involvement of cannabinoid CB(1) and CB(2) receptors in the Delta(9)-tetrahydrocannabinol-induced inhibition of natural killer activity

The impact of oral cannabis consumption during pregnancy on maternal spiral artery remodelling, fetal growth and offspring behaviour in mice

BACKGROUND

The use of cannabis during pregnancy is rising following its widespread legalization. Cannabidiol (CBD) is gaining popularity due to the public perception that it is safer than the psychoactive cannabis component Δ9-tetrahydrocannabinol (THC). However, while evidence underpins the harm of THC and cannabis smoke on fetal development, there is minimal research on the safety of CBD and oral cannabis. The current study aims to decipher the safety of oral CBD and THC use during pregnancy.

METHODS

Using a mouse model, we directly compared the effects of oral CBD and THC oil exposure (20 mg/kg body weight) from early to mid-gestation on implantation site remodelling and fetal growth. We examined offspring behaviour and metabolic activity using both traditional and automated cage systems. Lastly, using human and mouse immune cells we assessed how CBD and THC influence angiogenic factor production.

FINDINGS

We observed impaired maternal spiral artery remodelling in cannabis exposed mice and found that CBD and THC disrupt immune cell angiogenic factor production. Oral consumption of THC or CBD oil also resulted in significant fetal growth impairment and led to long-lasting sex-dependent consequences as male offspring exhibited altered aggression and metabolic activity while females had impaired spatial learning.

INTERPRETATION

Our results show that oral consumption of either CBD or THC oil during pregnancy in mice results in harm to the developing fetus and causes behavioural changes after birth.

FUNDING

The Michael G. DeGroote Centre for Medicinal Cancer Research, the Canadian Institutes of Health Research, and the Canadian Foundation for Innovation.

Cannabis use, oral dysbiosis, and neurological disorders

Cannabis (marijuana) is a leafy plant that has medical, recreational, and other uses. Cannabis is socially accepted and widely used throughout the United States. Though cannabis use is increasingly gaining popularity, studies detail the deleterious effects of chronic cannabis smoking on mental health, as well as the immunosuppressive properties of cannabinoids. Additionally, oral dysbiosis induced by cannabis smoking serves as a novel catalyst for neurological abnormalities, potentially possible through microbial translocation via the oral-brain axis. This review summarizes the effects and link of smoking cannabis on neurological abnormalities, immunity, and oral microbiome.

Modulation of pulmonary immune function by inhaled cannabis products and consequences for lung disease

The lungs, in addition to participating in gas exchange, represent the first line of defense against inhaled pathogens and respiratory toxicants. Cells lining the airways and alveoli include epithelial cells and alveolar macrophages, the latter being resident innate immune cells important in surfactant recycling, protection against bacterial invasion and modulation of lung immune homeostasis. Environmental exposure to toxicants found in cigarette smoke, air pollution and cannabis can alter the number and function of immune cells in the lungs. Cannabis (marijuana) is a plant-derived product that is typically inhaled in the form of smoke from a joint. However, alternative delivery methods such as vaping, which heats the plant without combustion, are becoming more common. Cannabis use has increased in recent years, coinciding with more countries legalizing cannabis for both recreational and medicinal purposes. Cannabis may have numerous health benefits owing to the presence of cannabinoids that dampen immune function and therefore tame inflammation that is associated with chronic diseases such as arthritis. The health effects that could come with cannabis use remain poorly understood, particularly inhaled cannabis products that may directly impact the pulmonary immune system. Herein, we first describe the bioactive phytochemicals present in cannabis, with an emphasis on cannabinoids and their ability to interact with the endocannabinoid system. We also review the current state-of-knowledge as to how inhaled cannabis/cannabinoids can shape immune response in the lungs and discuss the potential consequences of altered pulmonary immunity. Overall, more research is needed to understand how cannabis inhalation shapes the pulmonary immune response to balance physiological and beneficial responses with potential deleterious consequences on the lungs.

Cannabinoid receptor 2 plays a pro-tumorigenic role in non-small cell lung cancer by limiting anti-tumor activity of CD8+ T and NK cells

Cannabinoid (CB) receptors (CB1 and CB2) are expressed on cancer cells and their expression influences carcinogenesis in various tumor entities. Cells of the tumor microenvironment (TME) also express CB receptors, however, their role in tumor development is still unclear. We, therefore, investigated the role of TME-derived CB1 and CB2 receptors in a model of non-small cell lung cancer (NSCLC). Leukocytes in the TME of mouse and human NSCLC express CB receptors, with CB2 showing higher expression than CB1. In the tumor model, using CB1- (CB1 -/-) and CB2-knockout (CB2 -/-) mice, only deficiency of CB2, but not of CB1, resulted in reduction of tumor burden vs. wild type (WT) littermates. This was accompanied by increased accumulation and tumoricidal activity of CD8+ T and natural killer cells, as well as increased expression of programmed death-1 (PD-1) and its ligand on lymphoid and myeloid cells, respectively. CB2 -/- mice responded significantly better to anti-PD-1 therapy than WT mice. The treatment further increased infiltration of cytotoxic lymphocytes into the TME of CB2 -/- mice. Our findings demonstrate that TME-derived CB2 dictates the immune cell recruitment into tumors and the responsiveness to anti-PD-1 therapy in a model of NSCLC. CB2 could serve as an adjuvant target for immunotherapy.

“The Two Sides of the Same Coin”—Medical Cannabis, Cannabinoids and Immunity: Pros and Cons Explained

Cannabis, as a natural medicinal remedy, has long been used for palliative treatment to alleviate the side effects caused by diseases. Cannabis-based products isolated from plant extracts exhibit potent immunoregulatory properties, reducing chronic inflammatory processes and providing much needed pain relief. They are a proven effective solution for treatment-based side effects, easing the resulting symptoms of the disease. However, we discuss the fact that cannabis use may promote the progression of a range of malignancies, interfere with anti-cancer immunotherapy, or increase susceptibility to viral infections and transmission. Most cannabis preparations or isolated active components cause an overall potent immunosuppressive impact among users, posing a considerable hazard to patients with suppressed or compromised immune systems. In this review, current knowledge and perceptions of cannabis or cannabinoids and their impact on various immune-system components will be discussed as the “two sides of the same coin” or “double-edged sword”, referring to something that can have both favorable and unfavorable consequences. We propose that much is still unknown about adverse reactions to its use, and its integration with medical treatment should be conducted cautiously with consideration of the individual patient, effector cells, microenvironment, and the immune system.

The Interplay between the Immune and the Endocannabinoid Systems in Cancer

The therapeutic potential of Cannabis sativa has been recognized since ancient times. Phytocannabinoids, endocannabinoids and synthetic cannabinoids activate two major G protein-coupled receptors, subtype 1 and 2 (CB1 and CB2). Cannabinoids (CBs) modulate several aspects of cancer cells, such as apoptosis, autophagy, proliferation, migration, epithelial-to-mesenchymal transition and stemness. Moreover, agonists of CB1 and CB2 receptors inhibit angiogenesis and lymphangiogenesis in vitro and in vivo. Low-grade inflammation is a hallmark of cancer in the tumor microenvironment (TME), which contains a plethora of innate and adaptive immune cells. These cells play a central role in tumor initiation and growth and the formation of metastasis. CB2 and, to a lesser extent, CB1 receptors are expressed on a variety of immune cells present in TME (e.g., T cells, macrophages, mast cells, neutrophils, NK cells, dendritic cells, monocytes, eosinophils). The activation of CB receptors modulates a variety of biological effects on cells of the adaptive and innate immune system. The expression of CB2 and CB1 on different subsets of immune cells in TME and hence in tumor development is incompletely characterized. The recent characterization of the human cannabinoid receptor CB2-G_i signaling complex will likely aid to design potent and specific CB2/CB1 ligands with therapeutic potential in cancer.

The Immune Endocannabinoid System of the Tumor Microenvironment

Leukocytes are part of the tumor microenvironment (TME) and are critical determinants of tumor progression. Because of the immunoregulatory properties of cannabinoids, the endocannabinoid system (ECS) may have an important role in shaping the TME. Members of the ECS, an entity that consists of cannabinoid receptors, endocannabinoids and their synthesizing/degrading enzymes, have been associated with both tumor growth and rejection. Immune cells express cannabinoid receptors and produce endocannabinoids, thereby forming an “immune endocannabinoid system”. Although in vitro effects of exogenous cannabinoids on immune cells are well described, the role of the ECS in the TME, and hence in tumor development and immunotherapy, is still elusive. This review/opinion discusses the possibility that the “immune endocannabinoid system” can fundamentally influence tumor progression. The widespread influence of cannabinoids on immune cell functions makes the members of the ECS an interesting target that could support immunotherapy.

CB2 receptors regulate natural killer cells that limit allergic airway inflammation in a murine model of asthma

BACKGROUND

Allergic asthma is a chronic airway inflammatory disease involving the complementary actions of innate and adaptive immune responses. Endogenously generated cannabinoids acting via CB2 receptors play important roles in both homeostatic and inflammatory processes. However, the contribution of CB2-acting eicosanoids to the innate events preceding sensitization to the common house dust mite (HDM) allergen remains to be elucidated. We investigated the role of CB2 activation during allergen-induced pulmonary inflammation and natural killer (NK) cell effector function.

METHODS

Lung mucosal responses in CB2-deficient (CB2^-/- ) mice were examined and compared with wild-type (WT) littermates following intranasal exposure to HDM allergen.

RESULTS

Mice lacking CB2 receptors exhibited elevated numbers of pulmonary NK cells yet were resistant to the induction of allergic inflammation exemplified by diminished airway eosinophilia, type 2 cytokine production and mucus secretion after allergen inhalation. This phenomenon was corroborated when WT mice were treated with a CB2-specific antagonist that caused a pronounced inhibition of HDM-induced airway inflammation and goblet cell hyperplasia. Unexpectedly, the preponderance of NK cells in the lungs of CB2^-/- mice correlated with reduced numbers of group 2 innate lymphoid cells (ILC2s). Depletion of NK cells restored the allergen responsiveness in the lungs and was associated with elevated ILC2 numbers.

CONCLUSIONS

Collectively, these results reveal that CB2 activation is crucial in regulating pulmonary NK cell function, and suggest that NK cells serve to limit ILC2 activation and subsequent allergic airway inflammation. CB2 inhibition may present an important target to modulate NK cell response during pulmonary inflammation.

Biased Agonism and Biased Allosteric Modulation at the CB1 Cannabinoid Receptor

CB1 cannabinoid receptors (CB1Rs) are attractive therapeutic targets for numerous central nervous system disorders. However, clinical application of cannabinoid ligands has been hampered owing to their adverse on-target effects. Ligand-biased signaling from, and allosteric modulation of, CB1Rs offer pharmacological approaches that may enable the development of improved CB1R drugs, through modulation of only therapeutically desirable CB1R signaling pathways. There is growing evidence that CB1Rs are subject to ligand-biased signaling and allosterism. Therefore, in the present study, we quantified ligand-biased signaling and allosteric modulation at CB1Rs. Cannabinoid agonists displayed distinct biased signaling profiles at CB1Rs. For instance, whereas 2-arachidonylglycerol and WIN55,212-2 [(R)-(+)-[2,3-dihydro-5-methyl-3-(4-morpholinylmethyl)pyrrolo[1,2,3-de]-1,4-benzoxazin-6-yl]-1-napthalenylmethanone] showed little preference for inhibition of cAMP and phosphorylation of extracellular signal-regulated kinase 1/2 (pERK1/2), N-arachidonoylethanolamine (anandamide), methanandamide, CP55940 [2-[(1R,2R,5R)-5-hydroxy-2-(3-hydroxypropyl)cyclohexyl]-5-(2-methyloctan-2-yl)phenol], and HU-210 [11-hydroxy-Δ(8)-THC-dimethylheptyl] were biased toward cAMP inhibition. The small-molecule allosteric modulator Org27569 [5-chloro-3-ethyl-1H-indole-2-carboxylic acid [2-(4-piperidin-1-yl-phenyl)ethyl]amide] displayed biased allosteric effects by blocking cAMP inhibition mediated by all cannabinoid ligands tested, at the same time having little or no effect on ERK1/2 phosphorylation mediated by a subset of these ligands. Org27569 also displayed negative binding cooperativity with [(3)H]SR141716A [5-(4-chlorophenyl)-1-(2,4-dichloro-phenyl)-4-methyl-N-(piperidin-1-yl)-1H-pyrazole-3-carboxamide]; however, it had minimal effects on binding of cannabinoid agonists. Furthermore, we highlight the need to validate the reported allosteric effects of the endogenous ligands lipoxin A4 and pregnenolone at CB1Rs. Pregnenolone but not lipoxin A4 displaced [(3)H]SR141716A, but there was no functional interaction between either of these ligands and cannabinoid agonists. This study demonstrates an approach to validating and quantifying ligand-biased signaling and allosteric modulation at CB1Rs, revealing ligand-biased "fingerprints" that may ultimately allow the development of improved CB1R-targeted therapies.

Turning Over a New Leaf: Cannabinoid and Endocannabinoid Modulation of Immune Function

Cannabis is a complex substance that harbors terpenoid-like compounds referred to as phytocannabinoids. The major psychoactive phytocannabinoid found in cannabis ∆(9)-tetrahydrocannabinol (THC) produces the majority of its pharmacological effects through two cannabinoid receptors, termed CB1 and CB2. The discovery of these receptors as linked functionally to distinct biological effects of THC, and the subsequent development of synthetic cannabinoids, precipitated discovery of the endogenous cannabinoid (or endocannabinoid) system. This system consists of the endogenous lipid ligands N- arachidonoylethanolamine (anandamide; AEA) and 2-arachidonylglycerol (2-AG), their biosynthetic and degradative enzymes, and the CB1 and CB2 receptors that they activate. Endocannabinoids have been identified in immune cells such as monocytes, macrophages, basophils, lymphocytes, and dendritic cells and are believed to be enzymatically produced and released "on demand" in a similar fashion as the eicosanoids. It is now recognized that other phytocannabinoids such as cannabidiol (CBD) and cannabinol (CBN) can alter the functional activities of the immune system. This special edition of the Journal of Neuroimmune Pharmacology (JNIP) presents a collection of cutting edge original research and review articles on the medical implications of phytocannabinoids and the endocannabinoid system. The goal of this special edition is to provide an unbiased assessment of the state of research related to this topic from leading researchers in the field. The potential untoward effects as well as beneficial uses of marijuana, its phytocannabinoid composition, and synthesized cannabinoid analogs are discussed. In addition, the role of the endocannabinoid system and approaches to its manipulation to treat select human disease processes are addressed.

Differential role of cannabinoids in the pathogenesis of skin cancer

AIM

Cannabinoids (CB) like ∆(9)-tetrahydrocannabinol (THC) can induce cancer cell apoptosis and inhibit angiogenesis. However, the use of cannabinoids for the treatment of malignant diseases is discussed controversially because of their immunomodulatory effects which can suppress anti-tumor immunity. Here we investigated the role of exogenous and endogenous cannabinoids in mouse skin cancer.

MAIN METHODS

First we examined the effect of THC, which binds to CB receptors (CB1, CB2), on the growth of the mouse melanoma cell lines B16 and HCmel12 in vitro and in vivo in wild type (WT) and CB1/CB2-receptor deficient mice (Cnr1/2(-/-)). Next we evaluated the role of the endogenous cannabinoid system by studying the growth of chemically induced melanomas, fibrosarcoma and papillomas in WT and Cnr1/2(-/-) mice.

KEY FINDINGS

THC significantly inhibited tumor growth of transplanted HCmel12 melanomas in a CB receptor-dependent manner in vivo through antagonistic effects on its characteristic pro-inflammatory microenvironment. Chemically induced skin tumors developed in a similar manner in Cnr1/2(-/-) mice when compared to WT mice.

SIGNIFICANCE

Our results confirm the value of exogenous cannabinoids for the treatment of melanoma but do not support a role for the endogenous cannabinoid system in the pathogenesis of skin cancer.

Exposure of Adolescent Mice to Delta-9-Tetrahydrocannabinol Induces Long-Lasting Modulation of Pro- and Anti-Inflammatory Cytokines in Hypothalamus and Hippocampus Similar to that Observed for Peripheral Macrophages

Cannabis use is frequent among adolescents. Its main component, delta-9-tetrahydrocannabinol (THC), affects the immune system. We recently demonstrated that chronic exposure of adolescent mice to THC suppressed immunity immediately after treatment but that after a washout period THC induced a long-lasting opposite modulation towards a proinflammatory and T-helper-1 phenotype in adulthood. The main objective of this study was to investigate whether the same effect was also present in brain regions such as the hypothalamus and hippocampus. Thirty-three-day-old adolescent and 80-day-old adult male mice were used. Acute THC administration induced a similar reduction of macrophage proinflammatory cytokines and an IL-10 increase in adult and adolescent mice. THC did not affect brain cytokines in adult mice, but a proinflammatory cytokine decrease was evident in the adolescent brain. A similar effect was present in the hypothalamus and hippocampus after 10 days' THC administration. In contrast, when brain cytokines were measured 47 days after the final THC administration, we observed an inverted effect in adult mice treated as adolescents, i.e., IL-1β and TNF-α increased and IL-10 decreased, indicating a shift toward neuroinflammation. These data suggest that THC exposure in adolescence has long-lasting effects on brain cytokines that parallel those present in the periphery. This modulation may affect vulnerability to immune and behavioural diseases in adulthood.

Cannabis use by individuals with multiple sclerosis: effects on specific immune parameters

Cannabinoids affect immune responses in ways that may be beneficial for autoimmune diseases. We sought to determine whether chronic Cannabis use differentially modulates a select number of immune parameters in healthy controls and individuals with multiple sclerosis (MS cases). Subjects were enrolled and consented to a single blood draw, matched for age and BMI. We measured monocyte migration isolated from each subject, as well as plasma levels of endocannabinoids and cytokines. Cases met definition of MS by international diagnostic criteria. Monocyte cell migration measured in control subjects and individuals with MS was similarly inhibited by a set ratio of phytocannabinoids. The plasma levels of CCL2 and IL17 were reduced in non-naïve cannabis users irrespective of the cohorts. We detected a significant increase in the endocannabinoid arachidonoylethanolamine (AEA) in serum from individuals with MS compared to control subjects, and no significant difference in levels of other endocannabinoids and signaling lipids irrespective of Cannabis use. Chronic Cannabis use may affect the immune response to similar extent in individuals with MS and control subjects through the ability of phytocannabinoids to reduce both monocyte migration and cytokine levels in serum. From a panel of signaling lipids, only the levels of AEA are increased in individuals with MS, irrespective of Cannabis use or not. Our results suggest that both MS cases and controls respond similarly to chronic Cannabis use with respect to the immune parameters measured in this study.

Δ⁹-Tetrahydrocannabinol-induced anti-inflammatory responses in adolescent mice switch to proinflammatory in adulthood

Marijuana abuse is prominent among adolescents. Although Δ(9)-THC, one of its main components, has been demonstrated to modulate immunity in adults, little is known about its impact during adolescence on the immune system and the long-lasting effects in adulthood. We demonstrate that 10 days of Δ(9)-THC treatment induced a similar alteration of macrophage and splenocyte cytokines in adolescent and adult mice. Immediately at the end of chronic Δ(9)-THC, a decrease of proinflammatory cytokines IL- 1β and TNF-α and an increase of anti-inflammatory cytokine IL-10 production by macrophages were present as protein and mRNA in adolescent and adult mice. In splenocytes, Δ(9)-THC modulated Th1/Th2 cytokines skewing toward Th2: IFN-γ was reduced, and IL-4 and IL-10 increased. These effects were lost in adult animals, 47 days after the last administration. In contrast, in adult animals treated as adolescents, a perturbation of immune responses, although in an opposite direction, was present. In adults treated as adolescents, a proinflammatory macrophage phenotype was observed (IL-1β and TNF-α were elevated; IL-10 decreased), and the production of Th cytokines was blunted. IgM titers were also reduced. Corticosterone concentrations indicate a long-lasting dysregulation of HPA in adolescent mice. We measured blood concentrations of Δ(9)-THC and its metabolites, showing that Δ(9)-THC plasma levels in our mice are in the order of those achieved in human heavy smokers. Our data demonstrate that Δ(9)-THC in adolescent mice triggers immune dysfunctions that last long after the end of abuse, switching the murine immune system to proinflammatory status in adulthood.

Marijuana use and brain immune mechanisms

The recreational smoking of marijuana, or Cannabis sativa, has become widespread, including among adolescents. Marijuana contains a class of compounds known as phytocannabinoids that include cannabidiol (CBD) and Δ(9)-tetrahydrocannabinol (THC). THC is the major psychoactive component in marijuana, but also exhibits immunosuppressive activity. CBD, while not psychotropic, also modulates immune function, but its mechanism of action appears to differ from that of THC. Since both compounds are highly lipophilic, they readily passage the blood-brain barrier and access the central nervous system. Since CBD is not psychotropic, it has been considered as a candidate therapeutic compound for ablating neuropathological processes characterized by hyperinflammation. However, an unresolved question centers around the impact of these compounds on immune-competent cells within the CNS in relation to susceptibility to infection. There are accumulating data indicating that THC inhibits the migratory capability of macrophage-like cells resident in the CNS, such as microglia, toward nodes of microbial invasion. Furthermore, phytocannabinoids have been reported to exert developmental and long-term effects on the immune system suggesting that exposure to these substances during an early stage in life has the potential to alter the fundamental neuroimmune response to select microbial agents in the adult.

Monoacylglycerol lipase (MAGL) inhibition attenuates acute lung injury in mice

Endocannabinoid signaling is terminated by enzymatic hydrolysis, a process that, for 2-Arachidonoylglycerol (2-AG), is mediated by monoacylglycerol lipase (MAGL). The piperidine carbamate, 4-​nitrophenyl- ​4-​(dibenzo[d] [1,3]dioxol-​5-​yl (hydroxy) methyl) piperidine- 1-​carboxylate (JZL184), is a drug that inhibits MAGL and presents high potency and selectivity. Thus, JZL184 increases the levels of 2-AG, an endocannabinoid that acts on the CB₁ and CB₂ cannabinoid receptors. Here, we investigated the effects of MAGL inhibition, with a single dose (16 mg/kg, intraperitoneally (i.p.)) of JZL184, in a murine model of lipopolysaccharide (LPS) -induced acute lung injury (ALI) 6, 24 and 48 hours after the inflammatory insult. Treatment with JZL184 decreased the leukocyte migration into the lungs as well as the vascular permeability measured through the bronchoalveolar lavage fluid (BAL) and histological analysis. JZL184 also reduced the cytokine and chemokine levels in the BAL and adhesion molecule expression in the blood and BAL. The CB₁ and CB₂ receptors were considered involved in the anti-inflammatory effects of JZL184 because the AM281 selective CB₁ receptor antagonist (1-(2,4-dichlorophenyl)-5-(4-iodophenyl)-4-methyl-N-4-morpholinyl-1H-pyrazole-3-carboxamide) and the AM630 selective CB₂ receptor antagonist ([6-​iodo-​2-​methyl-​1-​[2-​(4-​morpholinyl)ethyl]-​1H-​indol-​3-​yl](4-​methoxyphenyl)-​methanone) blocked the anti-inflammatory effects previously described for JZL184. It was concluded that MAGL inhibition, and consequently the increase in 2-AG levels, produced anti-inflammatory effects in a murine model of LPS-induced ALI, a finding that was considered a consequence of the activation of the CB₁ and CB₂ receptors.

The importance of hydrogen bonding and aromatic stacking to the affinity and efficacy of cannabinoid receptor CB2 antagonist, 5-(4-chloro-3-methylphenyl)-1-[(4-methylphenyl)methyl]-N-[(1S,2S,4R)-1,3,3-trimethylbicyclo[2.2.1]hept-2-yl]-1H-pyrazole-3-carboxamide (SR144528)

Despite the therapeutic promise of the subnanomolar affinity cannabinoid CB2 antagonist, 5-(4-chloro-3-methylphenyl)-1-[(4-methylphenyl)methyl]-N-[(1S,2S,4R)-1,3,3-trimethylbicyclo[2.2.1]hept-2-yl]-1H-pyrazole-3-carboxamide (SR144528, 1), little is known about its binding site interactions and no primary interaction site for 1 at CB2 has been identified. We report here the results of Glide docking studies in our cannabinoid CB2 inactive state model that were then tested via compound synthesis, binding, and functional assays. Our results show that the amide functional group of 1 is critical to its CB2 affinity and efficacy and that aromatic stacking interactions in the TMH5/6 aromatic cluster of CB2 are also important. Molecular modifications that increased the positive electrostatic potential in the region between the fenchyl and aromatic rings led to more efficacious compounds. This result is consistent with the EC-3 loop negatively charged amino acid, D275 (identified via Glide docking studies) acting as the primary interaction site for 1 and its analogues.

Blockade of cannabinoid receptors reduces inflammation, leukocyte accumulation and neovascularization in a model of sponge-induced inflammatory angiogenesis

OBJECTIVE

Angiogenesis depends on a complex interaction between cellular networks and mediators. The endocannabinoid system and its receptors have been shown to play a role in models of inflammation. Here, we investigated whether blockade of cannabinoid receptors may interfere with inflammatory angiogenesis.

MATERIALS AND METHODS

Polyester-polyurethane sponges were implanted in C57Bl/6j mice. Animals received doses (3 and 10 mg/kg/daily, s.c.) of the cannabinoid receptor antagonists SR141716A (CB1) or SR144528 (CB2). Implants were collected at days 7 and 14 for cytokines, hemoglobin, myeloperoxidase, and N-acetylglucosaminidase measurements, as indices of inflammation, angiogenesis, neutrophil and macrophage accumulation, respectively. Histological and morphometric analysis were also performed.

RESULTS

Cannabinoid receptors expression in implants was detected from day 4 after implantation. Treatment with CB1 or CB2 receptor antagonists reduced cellular influx into sponges at days 7 and 14 after implantation, although CB1 receptor antagonist were more effective at blocking leukocyte accumulation. There was a reduction in TNF-α, VEGF, CXCL1/KC, CCL2/JE, and CCL3/MIP-1α levels, with increase in CCL5/RANTES. Both treatments reduced neovascularization. Dual blockade of cannabinoid receptors resulted in maximum inhibition of inflammatory angiogenesis.

CONCLUSIONS

Blockade of cannabinoid receptors reduced leukocyte accumulation, inflammation and neovascularization, suggesting an important role of endocannabinoids in sponge-induced inflammatory angiogenesis both via CB1 and CB2 receptors.

Endogenous lipid activated G protein-coupled receptors: emerging structural features from crystallography and molecular dynamics simulations

Class A G-protein coupled receptors (GPCRs) are thought to have a common topology that includes seven transmembrane alpha helices (TMHs) that are arranged to form a closed bundle. This bundle forms the ligand binding pocket into which ligands are commonly thought to enter via the extracellular milieu. This ligand approach direction makes sense for GPCRs that have small positively charged ligands, such as the beta-2-adrenergic or the dopamine D2 receptor. However, there is a growing sub-group of Class A GPCRs that bind lipid-derived endogenous ligands, such as the cannabinoid CB1 and CB2 receptors (with endogenous ligands, N-arachidonoylethanolamine (anandamide) and sn-2-arachidonylglycerol (2-AG)) and the S1P1-5 receptors (with endogenous ligand, sphingosine-1-phosphate). Even the widely studied Class A GPCR, rhodopsin, binds a highly lipophillic chromophore (11-cis-retinal). For these receptors, ligand approach from the extracellular milieu has seemed unlikely given that the ligands of these receptors readily partition into lipid or are actually synthesized in the lipid bilayer. The recent X-ray-crystal structure of the sub-type 1 sphingosine-1-phosphate receptor (S1P1) provides important information on the key structural variations that may be the hallmarks for a Class A GPCR that binds lipid-derived ligands. These include an extracellular domain that is closed off to the extracellular milieu and the existence of an opening between transmembrane helices that may serve as a portal for ligand entry via the lipid bilayer. This review examines structural aspects that the cannabinoid receptors may share with the S1P1 receptor based upon sequence homology. This review also examines experimental and simulation results that suggest ligand entry via a lipid portal is quite likely for this emerging sub-group.

Emerging role of the cannabinoid receptor CB2 in immune regulation: therapeutic prospects for neuroinflammation

There is now a large body of data indicating that the cannabinoid receptor type 2 (CB2) is linked to a variety of immune events. This functional relevance appears to be most salient in the course of inflammation, a process during which there is an increased number of receptors that are available for activation. Studies aimed at elucidating signal transduction events resulting from CB2 interaction with its native ligands, and of the role of exogenous cannabinoids in modulating this process, are providing novel insights into the role of CB2 in maintaining a homeostatic immune balance within the host. Furthermore, these studies suggest that the CB2 may serve as a selective molecular target for therapeutic manipulation of untoward immune responses, including those associated with a variety of neuropathies that exhibit a hyperinflammatory component.

Blocking the Cannabinoid Receptors: Drug Candidates and Therapeutic Promises

The CB1 and CB2 cannabinoid receptors have been described as two prime sites of action for endocannabinoids. Both the localization and pharmacology of these two G-protein-coupled receptors are well-described, and numerous selective ligands have been characterized. The physiological effects of Cannabis sativa (cannabis) and a throughout study of the endocannabinoid system allowed for the identification of several pathophysiological conditions--including obesity, dyslipidemia, addictions, inflammation, and allergies--in which blocking the cannabinoid receptors might be beneficial. Many CB1 receptor antagonists are now in clinical trials, and the results of several studies involving the CB1 antagonist lead compound rimonabant (SR141716A) are now available. This review describes the pharmacological tools that are currently available and the animal studies supporting the therapeutic use of cannabinoid receptor antagonists and inverse agonists. The data available from the clinical trials are also discussed.

Early maternal deprivation and neonatal single administration with a cannabinoid agonist induce long-term sex-dependent psychoimmunoendocrine effects in adolescent rats

Maternal deprivation [24h on postnatal day 9] might represent an animal model of schizophrenia and behavioural and neurochemical alterations observed in adulthood may be mediated by hippocampal impairments induced by abnormally increased glucocorticoids due to neonatal stress. We aimed to provide new data for psychoimmunoendocrine characterization of this animal model by evaluating its effects in adolescent rats of both genders. In previous studies we found that cannabinoid compounds counteracted the enhanced impulsivity of maternally deprived animals and that the cannabinoid receptor agonist WIN 55,212-2 showed neuroprotective properties in neonatal rats. So, we hypothesised that this compound could counteract at least some of the detrimental effects that we expected to find in maternally deprived animals. Accordingly, the drug was administered immediately after the maternal deprivation period. Maternally deprived males showed significantly decreased motor activity in the holeboard and the plus-maze. The cannabinoid agonist induced, exclusively in males, a significant anxiogenic-like effect, which was reversed by maternal deprivation. In the forced swimming test, both treatments independently induced depressive-like responses. Maternal deprivation reduced immunological function whereas the drug exerted tissue-dependent effects on the immune parameters analysed. Maternally deprived females showed reduced corticosterone levels whereas the cannabinoid agonist increased hormone concentration in all groups. In general, the results show detrimental effects of both treatments as well as intriguing interactions, notably in relation to emotional behaviour and certain immunological responses.

Cannabinoid receptors and endocannabinoids: evidence for new players

It is now well established that the psychoactive effects of Cannabis sativa are primarily mediated through neuronal CB1 receptors, while its therapeutic immune properties are primarily mediated through CB2 receptors. Two endocannabinoids, arachidonoylethanolamide and 2-arachidonoylglycerol, have been identified, their action on CB1 and CB2 thoroughly characterized, and their production and inactivation elucidated. However, many significant exceptions to these rules exist. Here we review the evidence suggesting that cannabinoids can modulate synaptic transmission, the cardiovascular system, and the immune system through receptors distinct from CB1 and CB2, and that an additional "independent" endocannabinoid signaling system that involves palmitoylethanolamide may exist.

Effects on the immune system

Marijuana and other exogenous cannabinoids alter immune function and decrease host resistance to microbial infections in experimental animal models and in vitro. Two modes of action by which delta9-tetrahydrocannabinol (THC) and other cannabinoids affect immune responses have been proposed. First, cannabinoids may signal through the cannabinoid receptors CB1 and CB2. Second, at sites of direct exposure to high concentrations of cannabinoids, such as the lung, membrane perturbation may be involved. In addition, endogenous cannabinoids or endocannabinoids have been identified and have been proposed as native modulators of immune functions through cannabinoid receptors. Exogenously introduced cannabinoids may disturb this homoeostatic immune balance. A mode by which cannabinoids may affect immune responses and host resistance maybe by perturbing the balance of T helper (Th)1 pro-inflammatory versus Th2 anti-inflammatory cytokines. While marijuana and various cannabinoids have been documented to alter immune functions in vitro and in experimental animals, no controlled longitudinal epidemiological studies have yet definitively correlated immunosuppressive effects with increased incidence of infections or immune disorders in humans. However, cannabinoids by virtue of their immunomodulatory properties have the potential to serve as therapeutic agents for ablation of untoward immune responses.

Indirect CB2 receptor and mediator-dependent stimulation of human whole-blood neutrophils by exogenous and endogenous cannabinoids

Immunomodulatory effects of endogenous and exogenous cannabinoids have been investigated in numerous studies, mostly performed with isolated cells or transformed cell lines, but only sparse data exist on human polymorphonuclear neutrophils (PMNs). We therefore investigated the respiratory burst reaction of human whole-blood PMNs under the influence of cannabinoids using flow cytometry. In their natural whole-blood milieu, a CB(2) receptor-dependent stimulation of the PMN respiratory burst was found at nanomolar concentrations of CP55 940 [(-)-cis-3-[2-hydroxy-4-(1,1-dimethylheptyl)phenyl]-trans-4-(3-hydroxypropyl)cyclohexanol] and methanandamide after a 3-h incubation period, whereas the short-living and rapidly hydrolyzed endogenous ligand anandamide did not alter the burst reaction of whole-blood PMNs under the same experimental conditions. The stimulatory cannabinoid effect was totally absent in isolated PMNs but could be transferred onto isolated PMNs by adding the cell-free low-molecular mass plasma fraction (<5000 Da) of cannabinoid-incubated blood, indicating an indirect mechanism depending on humoral products or mediators. Results of our further experiments suggest that products of the arachidonic acid metabolism are mediators of the cannabinoid-induced enhancement of the respiratory burst reaction of whole-blood PMNs.

Immunological aetiology of major psychiatric disorders: evidence and therapeutic implications

Historically, immunological research in psychiatry was based on empirical findings and early epidemiological studies indicating a possible relationship between psychiatric symptoms and acute infectious diseases. However, aetiopathological explanations for psychiatric disorders are no longer closely related to acute infection. Nevertheless, immune hypotheses have been discussed in schizophrenia, affective disorders and infantile autism in the last decades. Although the variability between the results of the epidemiological studies conducted to date is strikingly high, there is still some evidence that the immune system might play a role in the aetiopathogenesis of these three psychiatric diseases, at least in subgroups of patients. In anxiety disorders immunological research is still very much in its infancy, and the few and inconsistent data of immune changes in these patients are believed to reflect the influence of short- or long-term stress exposure. Nevertheless, there are also some hints raising the possibility that autoimmune mechanisms could interrupt neurotransmission, which would be of significance in certain patients with anxiety and panic disorders. Drug and alcohol (ethanol) dependence are not believed to be primarily influenced by an immunological aetiology. On the other hand, immune reactions due to different drugs of abuse and alcohol may directly or indirectly influence the course of concomitant somatic diseases. In different organic brain disorders the underlying somatic disease is defined as a primary immune or autoimmune disorder, for instance HIV infection or systemic lupus erythematosus (SLE). For other neurodegenerative disorders, such as Alzheimer's disease, immunoaetiopathological mechanisms are supported by experimental and clinical studies. Treatment strategies based on immune mechanisms have been investigated in patients with schizophrenia and affective disorders. Furthermore, some antipsychotics and most antidepressants are known to have direct or indirect effects on the immune system. Different immunotherapies have been used in autism, including transfer factor, pentoxifylline, intravenous immunoglobulins and corticosteroids. Immunosuppressive and/or immunomodulating agents are well established methods for treating the neuropsychiatric sequelae of immune or autoimmune disorders, for example AIDS and SLE. Therapeutic approaches in Alzheimer's disease also apply immunological methods such as strategies of active/passive immunisation and NSAIDs. Considering the comprehensive interactive network between mind and body, future research should focus on approaches linking targets of the different involved systems.

Cannabinoids and the immune system: potential for the treatment of inflammatory diseases?

Since the discovery of the cannabinoid receptors and their endogenous ligands, significant advances have been made in studying the physiological function of the endocannabinoid system. The presence of cannabinoid receptors on cells of the immune system and anecdotal and historical evidence suggesting that cannabis use has potent immuno-modulatory effects, has led to research directed at understanding the function and role of these receptors within the context of immunological cellular function. Studies from chronic cannabis smokers have provided much of the evidence for immunomodulatory effects of cannabis in humans, and animal and in vitro studies of immune cells such as T cells and macrophages have also provided important evidence. Cannabinoids can modulate both the function and secretion of cytokines from immune cells. Therefore, cannabinoids may be considered for treatment of inflammatory disease. This review article will highlight recent research on cannabinoids and how they interact with the immune system and also their potential use as therapeutic agents for a number of inflammatory disorders.

The use of cannabinoids in multiple sclerosis

Naturally occurring cannabinoids including Delta9-tetrahydrocannabinol and cannabidiol as well as endocannabinoids and synthetic cannabinoids may have a role in modulating experimental models of multiple sclerosis. Recent clinical studies to treat symptoms of multiple sclerosis have shown varying results, which may reflect issues relating to the way in which such studies were conducted. There is now increasing interest in the potential role of cannabinoids not only in symptom relief, but also for their possible neuroprotective actions.

2-Arachidonoyl-glycerol suppresses interferon-γ production in phorbol ester/ionomycin-activated mouse splenocytes independent of CB1 or CB2

2-Arachidonoyl-glycerol (2-AG), an endogenous ligand for cannabinoid receptor types 1 and 2 (CB1 and CB2), has previously been demonstrated to modulate immune functions including suppression of interleukin-2 expression and nuclear factor of activated T cells (NFAT) activity. The objective of the present studies was to investigate the effect of 2-AG on interferon-gamma (IFN-gamma) expression and associated upstream signaling events. Pretreatment of splenocytes with 2-AG markedly suppressed phorbol 12-myristate 13-acetate plus calcium ionophore (PMA/Io)-induced IFN-gamma secretion. In addition, 2-AG suppressed IFN-gamma steady-state mRNA expression in a concentration-dependent manner. To unequivocally determine the putative involvement of CB1 and CB2, splenocytes derived from CB1(-/-)/CB2(-/-) knockout mice were used. No difference in the magnitude of IFN-gamma suppression by 2-AG in wild-type versus CB1/CB2 null mice was observed. Time-of-addition studies revealed that 2-AG treatment up to 12 h post-cellular activation resulted in suppression of IFN-gamma, which was consistent with a time course conducted with cyclosporin A, an inhibitor of NFAT activity. Coincidentally, 2-AG perturbed the nuclear translocation of NFAT protein and blocked thapsigargin-induced elevation in intracellular calcium, suggesting that altered calcium regulation might partly explain the suppression of NFAT nuclear translocation and subsequent IFN-gamma production. Indeed, Io partially attenuated the 2-AG-induced suppression of PMA/Io-stimulated IFN-gamma production. Taken together, these data demonstrate that 2-AG suppresses IFN-gamma expression in murine splenocytes in a CB receptor-independent manner and that the mechanism partially involves suppression of intracellular calcium signaling and perturbation of NFAT nuclear translocation.

The nonpsychoactive component of marijuana cannabidiol modulates chemotaxis and IL-10 and IL-12 production of murine macrophages both in vivo and in vitro

Cannabidiol is the main nonpsychoactive component of marijuana. We examined the ability of in vivo and in vitro cannabidiol to interfere with the production of interleukin (IL)-12 and IL-10 by murine macrophages and to modulate macrophage chemotaxis. Cannabidiol added in vitro to peritoneal macrophages significantly increased IL-12 and decreased IL-10 production. The CB1 and CB2 receptor antagonists prevented this modulation. Macrophages from animals treated with cannabidiol at the dose of 30 mg kg(-1) either orally or i.p. produced higher levels of IL-12 and lower levels of IL-10 in comparison to controls, and the CB receptor antagonists did not prevent these effects. Cannabidiol dose-dependently decreased fMLP-induced chemotaxis of macrophages, and the CB2 receptor antagonist prevented this decrease.

Effect of cannabinoid ingestion (in the form of bhang) on the immune system of high school and university students

The discovery of cannabinoid receptors in the immune system and a family of endogenous ligands of these receptors provides a basis for understanding the cellular and molecular mechanisms of cannabis-induced immunotoxicity. The present study was conducted on 90 nonsmoker males of high school and university students living in Tanta city of matched age and socioeconomic lifestyle. They were divided into a control group (30 males) and a bhang user group (60 males), which used bhang by eating its sweet juice after boiling with a little water and drying in an oven, 'fola'. The bhang group was divided equally into two subgroups: subgroup 1 used bhang for 6-24 months (average 19 +/- 1.2) and subgroup 2 used bhang for 24-36 months (average 31 +/- 1.7). The immunotoxic effects of using bhang appeared in the form of a significant decrease in serum immunoglobulins (IgG and IgM), and C3 and C4 complement protein concentrations (P < 0.05). In addition, our results demonstrated a significant decrease in the absolute number of functionally different subsets of peripheral blood mononuclear lymphocytes, T and B lymphocytes and natural killer (NK) cells in bhang users as compared to controls (P < 0.05). Moreover, the fatty acid amide hydrolase (FAAH) showed significant decrease in bhang users as compared to controls and in subgroup 2 as compared to subgroup 1 (P < 0.05), indicating that the decrease in FAAH protein level is closely related to the duration of bhang use. Positive correlations were found between FAAH level and the absolute number of mononuclear cells (T, B lymphocytes and NK cells) among bhang user subgroups. The present study is the first study to report on the effect of bhang on complement proteins and immunoglobulins in humans. Our study revealed that bhang-induced immunotoxicity could be attributed to decrease in FAAH protein.

The THC-induced suppression of Th1 polarization in response to Legionella pneumophila infection is not mediated by increases in corticosterone and PGE2

T helper cell type 1 (Th1)-polarizing cytokines are induced by Legionella pneumophila infection and are suppressed by pretreatment with marijuana cannabinoids (CB). Glucocorticoids and prostaglandin E2(PGE2) are also reported to suppress Th1 polarization and are induced by Delta9-tetrahydrocannabinol (THC), so their role in the suppression of polarizing cytokines was examined. Injection of L. pneumophila or THC alone into BALB/c mice induced a rapid and transient rise in serum corticosterone (CS), and the injection of both agents significantly augmented the CS response, demonstrating that THC increased CS in Legionella-infected mice. Pretreatment with the CB receptor 1 (CB1) antagonist SR141716A had no effect on the THC-induced CS response, but CB2 antagonist (SR144528) treatment increased the CS response. To see if increased CS contributed to the down-regulation of Th1 cytokines, mice were pretreated with the steroid antagonist RU486 before THC injection and Legionella infection. The results showed that RU486 did not attenuate the THC-induced suppression of serum interleukin (IL)-12 or interferon-gamma (IFN-gamma). In addition to CS, THC injection increased urinary PGE2 metabolites, and the CB1 antagonist attenuated this increase. Although L. pneumophila infection increased urinary PGE2, THC pretreatment did not enhance this response; in addition, treatment with the cyclooxygenase inhibitor, indomethacin, did not block the THC-induced suppression of IL-12 and IFN-gamma. These results suggest that the elevation of CS and PGE2 does not account for the THC-induced attenuation of the Th1 cytokine response, and it is concluded that other suppressive mediators are induced by THC or that the drug acts directly on immune cells to suppress cytokine production.

Downregulation of class II transactivator (CIITA) expression by synthetic cannabinoid CP55,940

Cannabinoid receptors are known to be expressed in microglia; however, their involvement in specific aspects of microglial immune function has not been demonstrated. Many effects of cannabinoids are mediated by two G-protein coupled receptors, designated CB1 and CB2. We have shown that the CB1 receptor is expressed in microglia that also express MHC class II antigen (J. Neuroimmunol. 82 (1998) 13-21). In our present study, we have analyzed the effect of cannabinoid agonist CP55,940 on MHC class II expression on the surface of IFN-gamma induced microglial cells by flow cytometry. CP55,940 blocked the class II MHC expression induced by IFN-gamma. It has been shown that the regulation of class II MHC genes occurs primarily at the transcriptional level, and a non-DNA binding protein, class II transactivator (CIITA), has been shown to be the master activator for class II transcription. We find that mRNA levels of CIITA are increased in IFN-gamma induced EOC 20 microglial cells and that this increase is almost entirely eliminated by the cannabinoid agonist CP55,940. These data suggests that cannabinoids affect MHC class II expression through actions on CIITA at the transcriptional level.

Cannabinoids and opioids share cAMP pathway in rat splenocytes

In the present work we investigated on rat splenocytes long-term interactions between opioid and cannabinoid drugs in terms of a common regulation of cAMP intracellular pathway. Both morphine and the synthetic cannabinoid compound CP-55,940 inhibited in a concentration-dependent manner the intracellular cAMP level in splenocytes stimulated by forskolin. The in vitro combination of submaximal concentrations of the two drugs did not yield any additive effect on the inhibition induced by the two drugs. In splenocytes taken from rats chronically treated with CP-55,940 (0.2 mg/kg i.p., twice a day for 4.5 days) or morphine (5 mg/kg s.c., twice a day for 6.5 days) and in vitro exposed to either CP-55,940 or morphine, it was found a desensitisation and cross-desensitisation to the inhibitory effects on cAMP production induced by the two drugs. Binding experiments on the cannabinoid receptors level in spleen coronal sections after in vivo chronic administration of morphine, revealed that there was no changes in the binding of [H3]-CP-55,940. Thus, these results strengthen the hypothesis of cAMP as part of the common intracellular pathway shared by opiates and cannabinoids at immune cell level.

Role of cannabinoid CB1 receptors and tumor necrosis factor-alpha in the gut and systemic anti-inflammatory activity of SR 141716 (rimonabant) in rodents

(1) We investigated the effect of the cannabinoid CB1 receptor antagonist, SR 141716, on indomethacin-induced small intestine inflammation and Escherichia coli lipopolysaccharide (LPS)-induced plasma TNF-alpha (TNF) release in comparison to the cannabinoid CB2 receptor antagonist, SR 144528, in rodents. (2) In rats, indomethacin induced significant ulcer formation in the small intestine; this was accompanied by an increase in tissue TNF levels and myeloperoxidase (MPO) activity. SR 141716 prevented the ulcers and the rise in TNF levels (ID50 3.3, 0.4 mg kg-1, respectively) and MPO activity. SR 144528 prevented intestinal ulcers only. (3) The effect of SR 141716 against indomethacin-induced ulcers and increase of plasma TNF levels after LPS was also studied in wild-type and CB1 receptor knockout mice. Indomethacin induced intestinal ulcers in mice, but not tissue TNF production and MPO activity. SR 141716 reduced the ulcers to a similar extent in wild-type and CB1 receptor knockout mice. In rats and wild-type mice, but not in CB1 receptor knockout mice, SR 141716 inhibited the LPS-induced increase in plasma TNF levels. (4) These findings provide evidence that the indomethacin model of intestinal lesions differs in rat and mouse and support the existence of several mechanisms for the antiulcer activity of SR141716, the most important involving the inhibition of TNF production. The potent anti-inflammatory activity of SR141716 in rodents indicated its potential therapeutic interest in chronic immune-inflammatory diseases.

The relationships between substance abuse, psychosocial variables, and natural killer cell enumeration and function in HIV-infected and high-risk uninfected adolescents

This report examines the relationship between substance use, psychosocial stressors, and natural killer (NK) cell enumeration and function in HIV-infected and high-risk uninfected adolescents. We studied the association of demographic characteristics; self-report measures of alcohol, tobacco, and marijuana use; and self-report measures of psychosocial stressors (depressive symptoms, anxiety) with three immune outcomes: NK (CD3(-)CD16(+)CD56(+)) absolute counts, lytic units per peripheral blood mononuclear cells (PBMCs), and lytic units per NK cell. In addition, we determined the association of HIV disease stage, antiretroviral therapy (ART), CD4(+) T-cell count, and viral load with these outcomes in the subset of HIV-infected adolescents.

METHODS

This cross-sectional analysis reports on data collected during a longitudinal observational study of adolescents (the REACH Study). A cross-sectional analysis was performed with data from the first visit for each subject that met criteria for concurrent (within 3 days) assessment of NK number and function, substance use, and psychosocial data. The data set represented 501 subjects. Analyses were performed separately for the HIV-seropositive and seronegative adolescents. In the HIV-seronegative population, there were no significant predictors of NK cell count and only female gender was significantly associated with CD3(-)CD16(+)CD56(+) NK lytic units per PBMC. Analysis of the HIV-seronegative cohort also showed that black race was significantly associated with higher lytic units per NK cell.

RESULTS

In HIV-seropositive adolescents, we observed an association of female gender with lower NK cell number and lytic units per PBMC, but not with lytic units per NK cells. Current use of one or two antiretroviral drugs was predictive of lower NK numbers. This drug effect was also noted in the functional assay per PBMC but not per NK cell. Increasing worry scores and no marijuana use over the past 3 months were associated with lower functional NK measures per PBMC in HIV-seropositive youth. Laboratory-confirmed recent marijuana use was highly predictive of increased lytic activity calculated per NK cell. These effects were not observed in similar analyses of data from HIV-seronegative adolescents. Depressive symptoms, assessed with an epidemiologic screening tool, were not found to be predictive of NK cell number or function in either the HIV-seronegative or the HIV-seropositive subset. These findings document associations between substance abuse, psychosocial variables, and NK numbers and function in adolescents.

Microbial infections, immunomodulation, and drugs of abuse

The use of recreational drugs of abuse has generated serious health concerns. There is a long-recognized relationship between addictive drugs and increased levels of infections. Studies of the mechanisms of actions of these drugs became more urgent with the advent of AIDS and its correlation with abused substances. The nature and mechanisms of immunomodulation by marijuana, opiates, cocaine, nicotine, and alcohol are described in this review. Recent studies of the effects of opiates or marijuana on the immune system have demonstrated that they are receptor mediated, occurring both directly via specific receptors on immune cells and indirectly through similar receptors on cells of the nervous system. Findings are also discussed that demonstrate that cocaine and nicotine have similar immunomodulatory effects, which are also apparently receptor mediated. Finally, the nature and mechanisms of immunomodulation by alcohol are described. Although no specific alcohol receptors have been identified, it is widely recognized that alcohol enhances susceptibility to opportunistic microbes. The review covers recent studies of the effects of these drugs on immunity and on increased susceptibility to infectious diseases, including AIDS.

Pharmacological characterisation of cannabinoid receptors inhibiting interleukin 2 release from human peripheral blood mononuclear cells

The effects of a range of cannabinoid receptor agonists and antagonists on phytohaemagglutinin-induced secretion of interleukin-2 from human peripheral blood mononuclear cells were investigated. The nonselective cannabinoid receptor agonist WIN55212-2 ((R)-(+)-[2,3-dihydro-5-methyl-3-[4-morpholinylmethyl]pyrrolo[1,2,3-de]1,4-benzoxazin-6-yl](1-naphthyl) methanone mesylate) and the selective cannabinoid CB(2) receptor agonist JWH 015 ((2-methyl-1-propyl-1H-indol-3-yl)-1-napthalenylmethanone) inhibited phytohaemagglutinin (10 microg/ml)-induced release of interleukin-2 in a concentration-dependent manner (IC(1/2max), WIN55212-2=8.8 x 10(-7) M, 95% confidence limits (C.L.)=2.2 x 10(-7)-3.5 x 10(-6) M; JWH 015=1.8 x 10(-6) M, 95% C.L.=1.2 x 10(-6)-2.9 x 10(-6) M, n=5). The nonselective cannabinoid receptor agonists CP55,940 ((-)-3-[2-hydroxy-4-(1,1-dimethyl-hepthyl)-phenyl]4-[3-hydroxypropyl]cyclo-hexan-1-ol), Delta(9)-tetrahydrocannabinol and the selective cannabinoid CB(1) receptor agonist ACEA (arachidonoyl-2-chloroethylamide) had no significant (P>0.05) inhibitory effect on phytohaemagglutinin-induced release of interleukin-2. Dexamethasone significantly (P<0.05) inhibited phytohaemagglutinin-induced release of interleukin-2 in a concentration-dependent manner (IC(1/2max)=1.3 x 10(-8) M, 95% C.L.=1.4 x 10(-9)-3.2 x 10(-8) M). The cannabinoid CB(1) receptor antagonist SR141716A (N-(piperidin-1-yl)-5-(4-chlorophenyl)-1-(2,4-dichlorophenyl)-4-methyl-1H-pyrazole-3-carboxamide hydrochloride) (10(-6) M) did not antagonise the inhibitory effect of WIN55212-2 whereas the cannabinoid CB(2) receptor antagonist SR144528 (N-(1,S)-endo-1,3,3-trimethyl bicyclo(2,2,1)heptan-2-yl)-5-(4-chloro-3-methylphenyl)-1-(4-methylbenzyl)-pyrazole-3-carboxamide) antagonised the inhibitory effect of WIN55212-2 (pA(2)=6.3+/-0.1, n=5). In addition, CP55,940 (10(-6) M) and Delta(9)-tetrahydrocannabinol (10(-6) M) also antagonised the inhibitory effects of WIN55212-2 (pA(2)=6.1+/-0.1, n=5 and pA(2)=6.9+/-0.2, n=5). In summary, WIN55,212-2 and JWH 015 inhibited interleukin-2 release from human peripheral blood mononuclear cells via the cannabinoid CB(2) receptor. In contrast, CP55,940 and Delta(9)-tetrahydrocannabinol behaved as partial agonists/antagonists in these cells.

Endocannabinoids induce ileitis in rats via the capsaicin receptor (VR1)

Intraluminal administration of the endocannabinoids N-arachidonoyl-ethanolamine (anandamide) and 2-arachidonoylglycerol (2-AG) causes inflammation similar to that caused by Clostridium difficile toxin A in the rat ileum. The effects of anandamide and 2-AG were significantly inhibited by pretreatment with the specific capsaicin receptor (vanilloid receptor subtype 1; VR1) antagonist capsazepine. Pretreatment with the CB1 and CB2 cannabinoid receptor antagonists N-piperidino-5-(4-chlorophenyl)-1-(2,4-dichlorophenyl)-4-methyl-3-pyrazole-carboxamide (SR141716) and N-[1S)-endo-1,3,3-trimethylbicyclo[2.2.1]heptan-2-yl]-5-(4-chloro-3-methylphenyl)-1-(4-methylbenzyl)-pyrazole-3-carboxamide (SR144528) did not affect the responses to anandamide. It has previously been shown that intraluminal toxin A stimulates substance P (SP) release from primary sensory neurons and that pretreatment with SP receptor [neurokinin (NK)-1 receptor] antagonists inhibits the inflammatory effects of toxin A. Anandamide stimulated SP release and this was blocked by capsazepine pretreatment. Also, pretreatment with the specific NK-1 receptor antagonist (2S,3S)-3-([3,5-bis[trifluoromethyl)phenyl]methoxy)-2-phenylpiperidine (L-733,060) significantly inhibited the inflammatory effects of both toxin A and anandamide. Toxin A increased tissue concentrations of anandamide and 2-AG in the ileum, and these effects were enhanced after pretreatment with inhibitors of fatty acid amide hydrolase, a major endocannabinoid-degrading enzyme. The toxin A-stimulated release of anandamide but not 2-AG was selective over their congeners. These results demonstrate that the endocannabinoids anandamide and 2-AG stimulate intestinal primary sensory neurons via the capsaicin VR1 receptor to release SP, resulting in enteritis, and that endocannabinoids may mediate the inflammatory effects of toxin A.

Delta 9-Tetrahydrocannabinol regulates Th1/Th2 cytokine balance in activated human T cells

Human leukocytes express cannabinoid (CB) receptors, suggesting a role for both endogenous ligands and Delta 9-tetrahydrocannabinol (THC) as immune modulators. To evaluate this, human T cells were stimulated with allogeneic dendritic cells (DC) in the presence or absence of THC (0.625-5 microg/ml). THC suppressed T cell proliferation, inhibited the production of interferon-gamma and shifted the balance of T helper 1 (Th1)/T helper 2 (Th2) cytokines. Intracellular cytokine staining demonstrated that THC reduced both the percentage and mean fluorescence intensity of activated T cells capable of producing interferon-gamma, with variable effects on the number of T cells capable of producing interleukin-4. Exposure to THC also decreased steady-state levels of mRNA encoding for Th1 cytokines, while increasing mRNA levels for Th2 cytokines. The CB2 receptor antagonist, SR144528, abrogated the majority of these effects. We conclude that cannabinoids have the potential to regulate the activation and balance of human Th1/Th2 cells by a CB2 receptor-dependent pathway.

The cannabinoid receptors

Cannabinoid receptors were named because they have affinity for the agonist delta9-tetrahydrocannabinol (delta9-THC), a ligand found in organic extracts from Cannabis sativa. The two types of cannabinoid receptors, CB1 and CB2. are G protein coupled receptors that are coupled through the Gi/o family of proteins to signal transduction mechanisms that include inhibition of adenylyl cyclase, activation of mitogen-activated protein kinase, regulation of calcium and potassium channels (CB1 only), and other signal transduction pathways. A class of the eicosanoid ligands are relevant to lipid-mediated cellular signaling because they serve as endogenous agonists for cannabinoid receptors, and are thus referred to as endocannabinoids. Those compounds identified to date include the eicosanoids arachidonoylethanolamide (anandamide), 2-arachidonoylglycerol and 2-arachidonylglyceryl ether (noladin ether). Several excellent reviews on endocannabinoids and their synthesis, metabolism and function have appeared in recent years. This paper will describe the biological activities, pharmacology, and signal transduction mechanisms for the cannabinoid receptors, with particular emphasis on the responses to the eicosanoid ligands.

Cloning and molecular characterization of the rat CB2 cannabinoid receptor

The rat peripheral cannabinoid receptor (rCB2) was cloned from a Sprague-Dawley rat spleen cDNA library and when translated, encodes a protein of 410 amino acids. Alignment of rCB2 with mouse (mCB2) and human (hCB2) peripheral cannabinoid receptors reveals a high degree of homology except in the carboxy terminus where rCB2 is 50 and 63 residues longer than hCB2 and mCB2, respectively. PCR screening and sequencing of rat genomic DNA showed that rCB2 is encoded by three exons interrupted by two introns, one of which is polymorphic and contains a 209 base pair B2 (SINE) element. By Northern hybridization and ribonuclease protection assay (RPA), rCB2 mRNA was detected in rat spleen, testis, thymus and lung but not in rat brain, heart, kidney or liver. Like hCB2 and mCB2 receptors, rCB2 activates mitogen-activated protein kinase when it is stably expressed in Chinese Hamster Ovary (CHO) cells. The importance of the carboxy terminus in regulating CB2 receptor desensitization and internalization is well-established. Thus, the profound differences identified in this region of the CB2 receptor between species mandates caution when extrapolating experimental results from non-human models to the effects of chronic CB2 receptor stimulation in humans.

Selective cannabinoid CB1 receptor-mediated inhibition of inducible nitric oxide synthase protein expression in C6 rat glioma cells

We have studied the effects of two cannabinoid receptor agonists, WIN 55,212-2 and cannabinol, on nitric oxide (NO) production and inducible nitric oxide synthase (iNOS) expression in the C6 glioma cell line. After 24 h of lipopolysaccharide (LPS) (1 microg/mL) and interferon-gamma (IFN-gamma) (300 U/mL) stimulation, a significant increase in NO production, evaluated as nitrite, was observed in the culture medium. WIN 55,212-2 (0.1-10000 nM) and cannabinol (0.3-30000 nM), dose-dependently inhibited nitrite production showing a different potency (WIN 55,212-2 EC(50): 4.2 nM; cannabinol EC(50): 700 nM). WIN 55,212-2 (100 nM), given concomitantly to the stimulus also inhibited iNOS expression but had no effect when added to the cells 2 h after LPS/IFN-gamma, indicating a possible interference at the protein synthesis level or at an earlier step, as gene transcription. The cannabinoid CB1 receptor antagonist, SR141716A (0.1-100 nM), but not the cannabinoid CB2 receptor antagonist, SR144528 (0.1-100 nM), reduced in a dose-related manner WIN 55,212-2-and cannabinol-induced inhibition of nitrite production. SR141161A also reversed the WIN 55,212-2-induced inhibition of iNOS expression. These data suggest that selective cannabinoid CB1 receptor activation, by inhibiting iNOS expression and NO overproduction in glial cells, might be helpful in NO-mediated inflammation leading to neurodegeneration.